U.S. patent application number 10/340030 was filed with the patent office on 2003-07-17 for universal joint.
Invention is credited to Matthews, Timothy Robert.
Application Number | 20030134682 10/340030 |
Document ID | / |
Family ID | 9929034 |
Filed Date | 2003-07-17 |
United States Patent
Application |
20030134682 |
Kind Code |
A1 |
Matthews, Timothy Robert |
July 17, 2003 |
Universal joint
Abstract
A universal joint comprises a first attachment element having
first and second engagement regions, a second attachment element
having third and fourth engagement regions and a cruciform element.
The cruciform element engages with the first to fourth engagement
regions and has a bearing material is fixed thereon such that
relative movement occurs at the interface between the radially
outermost surface of the bearing material and the co-pending parts
of the engagement regions.
Inventors: |
Matthews, Timothy Robert;
(Pankridge, GB) |
Correspondence
Address: |
REISING, ETHINGTON, BARNES, KISSELLE, P.C.
P O BOX 4390
TROY
MI
48099-4390
US
|
Family ID: |
9929034 |
Appl. No.: |
10/340030 |
Filed: |
January 10, 2003 |
Current U.S.
Class: |
464/132 |
Current CPC
Class: |
F16D 3/382 20130101;
F16D 3/40 20130101 |
Class at
Publication: |
464/132 |
International
Class: |
F16D 003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 14, 2002 |
GB |
0200748.2 |
Claims
1. A universal joint comprising: a first attachment element having
first and second engagement regions; a second attachment element
having third and fourth engagement regions; and a cruciform element
engaging with the first to fourth engagement regions, wherein a
bearing material is fixed on the cruciform such that relative
movement occurs at the interface between the radially outermost
surface of the bearing material and the co-operating parts of the
engagement regions.
2. A universal joint according to claim 1, wherein the cruciform
element comprises four arms and the bearing material substantially
fills the volume defined by an outer surface of one of the arms and
an inner surface of a respective attachment region.
3. A universal joint according to claim 2, wherein the bearing
material extends over An end face of each arm of the cruciform
element thereby providing an end face thrust bearing.
4. A universal joint according to claim 2, wherein at least one of
the arms of the cruciform extends within a thermally conductive
bearing cap.
5. A universal joint according to claim 3, wherein at least one of
the arms of the cruciform extends within a thermally conductive
bearing cap.
6. A universal joint according to claim 2, wherein at least one of
the arms of the cruciform has an annular seal groove formed
therein.
7. A universal joint according to claim 1, wherein one or more of
the first to fourth attachment regions comprise a bearing cap that
encloses the bearing material.
8. A universal joint according to claim 1, wherein the first and
second engagement regions of the first attachment element and the
third and fourth engagement regions of the second attachment
element define respective axially aligned passages.
9. A universal joint according to claim 1, wherein the bearing
material comprises a solid low friction and/or low maintenance
material.
10. A universal joint comprising a first element rotatably
supported in a recess defined by a second element, wherein a
bearing material is fixed to the first element, such that relative
motion occurs between the bearing material and the second
element.
11. A universal joint comprising a cruciform member having four
limbs, a first connecting element being rotatably engaged with a
first opposing pair of the cruciform limbs and a second connecting
element being rotatably engaged with a second opposing pair of the
cruciform limbs, wherein each of the cruciform limbs carries a
bearing material disposed between the respective limb and
connecting element.
Description
BACKGROUND TO THE INVENTION
[0001] Universal joints generally known in the art comprise first
and second attachment elements connected to one another by way of
an intermediate cruciform member. The cruciform member is generally
rotationally engaged with engagement regions of the attachment
elements such that relative rotation may occur between each of the
attachment elements and the cruciform member. This allows
rotational motion to be transmitted from a first rotating element
to a second rotating element interconnected by the universal joint
where the axes of rotation may not be, or remain, coaxial.
[0002] In prior art arrangements a bearing material is generally
provided that is either free to rotate with respect to both the
cruciform and the engagement regions, or is fixed to the engagement
regions. This means that relative motion can occur at the interface
between the cruciform element and the bearing material, giving rise
to heating of the cruciform element. However, where the bearing
material is synthetic, it often exhibits low thermal conductivity.
This means that there is no thermal path for the cruciform element
to lose its heat, and consequently the cruciform element can become
thermally stressed. This in turn can give rise to a shorter service
life and can create unnecessary loads on the bearings due to
thermal expansion.
SUMMARY OF THE INVENTION
[0003] According to the present invention there is provided a
universal joint comprising:
[0004] a first attachment element having first and second
engagement regions;
[0005] a second attachment element having third and fourth
engagement regions; and
[0006] a cruciform element engaging with the first to fourth
engagement regions, and in which a bearing material is fixed on the
cruciform such that relative movement occurs at the interface
between the radially outermost surface of the bearing material and
the co-operating parts of the engagement regions.
[0007] It is thus possible to provide a universal joint in which
the bearing material is fixed to the cruciform, thereby ensuring
that relative motion occurs at the interface between the bearing
material and the engagement regions.
[0008] This modification to the design confers several
advantages:
[0009] 1) Any heat resulting from frictional forces is generated
over a larger contact area.
[0010] 2) The cruciform is thermally insulated from the region
where the heat is created by virtue of the bearing material.
[0011] 3) Heat generated at the interface with the engagement
regions is conducted away via the engagement regions to the
attachment elements.
[0012] 4) The bearing material, being formed on the cruciform
element rather than on an attachment element, is better
supported.
[0013] 5) As only a single item, the cruciform element, requires
processing to fix the bearing material thereon, processing time and
costs are reduced.
[0014] Preferably the attachment elements are in the form of
plates, flanges, webs or the like having attachment regions
defining axially aligned passages.
[0015] The attachment regions may form bearing caps which serve to
enclose the bearing material.
[0016] Advantageously the bearing material is a low friction and/or
low maintenance material which substantially fills the volume
defined by the outer surface of one of the arms of the cruciform
element and the inner surface of the attachment region. Thus the
bearing is solid. That is there are no roller bearings or ball
bearings. This gives rise to a universal joint which is
substantially maintenance free throughout its operating life.
[0017] Preferably the bearing material extends over an end face of
each arm of the cruciform in order to provide an end face thrust
bearing.
[0018] According to a second aspect of the present invention there
is provided a joint comprising a first element rotatably supported
in a recess defined by a second element, wherein a bearing material
is fixed to the first element, such that relative motion occurs
between the bearing material and the second element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The present invention will further be described, by way of
example, with reference to the accompanying drawings, in which:
[0020] FIG. 1 is a perspective view of a universal joint;
[0021] FIG. 2 is a cross section of a cruciform constituting an
embodiment of the present invention;
[0022] FIG. 3 shows a cross section through one possible embodiment
of an arm of a cruciform in accordance with the present
invention;
[0023] FIG. 4 shows a cross section through an alternative
embodiment of an arm of a cruciform in accordance with the present
invention; and
[0024] FIG. 5 compares and contrasts the present invention with
equivalent prior art arrangements.
DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
[0025] A universal joint is schematically illustrated in FIG. 1.
The universal joint allows rotational movement to be transmitted
between a first attachment element 2 and a second attachment
element, generally indicated 4, by way of an intermediate cruciform
member 6 which is part visible in FIG. 1. In general each of the
first and second attachment elements comprises a backing plate or
similar support member 8 which has first and second engagement
regions 10 and 12 forming axially aligned cup shaped recesses
which, in use, engage opposing limbs of the cruciform element
6.
[0026] Each of the attachment elements allows relative rotation to
occur between it and the cruciform 6. This in turn allows
rotational motion to be transmitted from a first rotating element
to a second rotating element interconnected by the universal joint
where the axes of rotation may not remain coaxial.
[0027] FIG. 2 schematically illustrates a cruciform in accordance
with the present invention. In general, the cruciform comprises a
central portion 20 from which four arms 22, 24, 26 and 28 extend.
In general the cruciform exhibits four fold rotational symmetry.
Each arm is preferably integrally formed with the cruciform and, in
use, extends into a respective one of the engagement regions within
the universal joint. The joint may be subjected to high loads or
high rotational rates, and consequently it is necessary to provide
a bearing between the cruciform element and the first and second
attachment elements. In an embodiment of the present invention,
this is provided by a solid low friction material which is bonded
to the cruciform 20. Thus, traditional bearings are avoided in this
design.
[0028] The cruciform 20 may be cast, molded, forged or machined
from an appropriate material. Indeed, the surface finish of the
cruciform may be deliberately made rough in order to provide
enhanced bonding between the bearing material 30 applied to the
limbs of the cruciform and the material of the cruciform itself.
The bearing material 30 may be applied by bonding, spraying or
molding it on to the cruciform and then curing the material in
order to harden it.
[0029] Each limb of the cruciform 20 may have a substantially
cylindrical profile, as shown in FIG. 3, or may have a seal groove
32 formed in the vicinity of the centre body of the cruciform, as
shown in FIG. 4.
[0030] FIG. 5 schematically compares the present invention with
prior art arrangements. Thus, for simplicity, the arms of the
cruciform shown in FIG. 5 have different bearing arrangements
illustrated thereon. It should be appreciated that this is for
illustrational purposes only, and in use, each of the arms of the
cruciform is likely to have the same bearing arrangement formed
thereon.
[0031] As shown in FIG. 5, the first arm labelled A merely shows an
embodiment of the present invention in which the arm has the
bearing material 30 permanently affixed thereto. The arm C shown in
FIG. 5 schematically illustrates the bearing arrangement at its
in-use position. Thus, an arm 40 having the bearing material 30
permanently bonded thereto extends within a bearing cap 42 within
one of the 1st to 4th engagement regions defined by the attachment
elements. The low friction material 30 extends along an end wall 44
of the arm 40 in order to provide a thrust surface. The bearing cap
42 is sealed by a ring seal 46 held within a seal groove 48. All
relative rotational movement occurs at the interface between the
radially outward surface of the bearing material 30 and the
radially innermost surface of the bearing cap 42. Thus the
cruciform element is both thermally insulated from the heat
generated at this interface (by virtue of the low friction material
30) and also the heat generated by relative motion can be conducted
to the bearing cap and dissipated.
[0032] Limbs B and D of FIG. 5 schematically illustrate known
bearing arrangements where the low friction material 30 is bonded
to a bearing cap 60. The limbs B and D shown in FIG. 5 are
essentially identical, except for the fact that D has a end
seal.
[0033] FIG. 5 is drawn to scale, and it can be seen that for an
equivalent interface area the bearing formed on limb C is smaller
than that formed on limbs B and D. Indeed, the bearing cap of limb
D is shown in dotted outline 62 on limb C by way of comparison.
[0034] It is thus clear that the present invention, whereby the low
friction material is bonded to the cruciform element, confers many
advantages. For example, the key between the low friction material
and the substrate to which it is bonded is simplified because the
material is now being applied to an external rather than an
internal surface and thus it can be molded, sprayed or bonded to
the external surface. The arrangement allows for a single piece
cruciform bearing assembly including end face thrust bearings. The
arrangement also provides for easier manufacturing of the bearing
surfaces, as some composite or ceramic materials that may be used
require specific machining operations that can be more reliably
performed on an external surface than an internal surface.
Similarly, the ease of machining allows tolerances to be better
controlled.
[0035] As regards performance improvements, the present invention
maximises the bearing area of the plastic rubbing face for a given
size of bearing assembly. This in turn reduces stresses generated
in the joint, reduces the overall size and weight cost of the
joint, reduces wear and improves life and performance of the joint.
Furthermore, as noted hereinbefore, the rubbing surface on the
outside diameter of the low friction plastic allows better heat
transfer away from the cruciform rubbing surfaces. This in effect
allows increased power transmission capacity for a given joint
size.
* * * * *